This invention relates to a method and apparatus for the culture of cells. The cells to be cultured in this invention are prokaryotic and eukaryotic cells such as bacteria, yeast, plant, animal and human cells. These cells may be derived in any manner, that is, isolated from nature, mutated, in the naturally-occurring form, genetically engineered or modified, transformed or non-transformed, hybrids formed by fusion between portions of cells or whole cells of the same or different species. These cells may be attached to the substrate, grown in suspension, or in suspension attached to another substrate, such as microcarrier bead. The cultures may consist of a single cell line or a plurality of cell lines of the same or different species.
Conventionally, cells have been attached to and grown on the interior surface of glass or plastic roller bottles or tubes or on culture plates. This approach does not permit high-density growth of cells and requires large amounts of nutrient medium, in most cases. Use of these systems is also labor intensive.
U.S. Pat. Nos. 4,189,534 and 4,266,032 describe the growth of cells on tiny beads referred to in the art as microcarrier. Microcarrier systems have several disadvantages, such as cell damage from collision of beads, mingling of the desired cell product with the nutrient medium, cell fragments and other contaminants, and the difficulty of achieving continuous production of the desired product.
It is also known that cells may be grown on or near hollow or solid fibers. See U.S. Pat. Nos. 3,883,393; 3,997,396; and 4,087,327; 4,220,725; 4,391,912 also J. Feder and W. R. Tolbert, "The Large-Scale Cultivation of Mammalian Cells", Scientific American, Vol. 248, No. 1 and Amicon Technical Data Publication Number 442C, "Vitafiber.TM. Artificial Capillary Systems for Tissue Culture". Typically the nutrient medium is passed through the hollow fibers and diffuses through the lumen thereof into the cell growth space and extracapillary space bounded by an envelope. These capillaries are susceptible to mechanical vibration and shock. The location of the cells is not closely constrained and the cells most distal from the fibers may not be well nourished. Large volumes of nutrient are typically utilized.
U.S. Pat. No. 4,225,671 describes a cell culture apparatus in which a stack of parallel flat membranes defines separate, typically alternating, cell culture medium, and cell growth spaces. These membranes are spaced widely apart (2 mm), so excessive quantities of nutrient must be provided to ensure the nourishment of the cells most distal from the membrane. Since the membranes are supported only at their edges, the maximum surface area of each membrane is limited by the tensile strength of the membrane. Thus, production capacity is limited. In addition the membrane is not designed to restrict the flow of the cell product into the nutrient medium and the product is collected in that medium. Because the cell product is mingled with the culture medium, product, recovery and purification is complex and results in a low yield of product.
U.S. Pat. No. 3,948,732 shows a spacer structure which is convoluted to offer internal support to the substrate surfaces. It does not, however, recognize the importance of a fluid path separate from that of the nutrient medium.
One object of the invention is to provide a closed sterile system for cell culture in order to prevent both exposure of personnel to the cells and the contamination or infection of the cell culture by wild strains entering from the outside environment.
Another object of the invention is to provide a system for cell culture which more closely approximates a continuous system than those known previously, thus increasing the average or steady-state output of product and minimizing opportunities for contamination.
Another object of the invention is to simulate the supply of nutrient to and exchange of gases by cells in vivo, wherein cells are typically less than 200 microns from the capillaries, the sources of nutrients and respiratory gases.
Another object of the invention is to provide a cell culture assembly in which the maximum distance between a cell and the nearest source of nutrients and dissolved gases approximates that typical of the cells in vivo.
Another object of the invention is to provide a cell culture assembly which can be economically manufactured.
Another object of the invention is to provide a cell culture assembly and cell culture system which lends itself to the growth of cells at high densities.
Another object of the invention is to provide a cell culture assembly and cell culture system in which fluctuations in cell growth and production of the desired product are reduced.
Another object of the invention is to provide a cell culture system in which nutrient supply, heat transfer, gas transfer, cell growth and product collection functions are integrated.
Another object of the invention is to provide a cell culture system in which those functions are performed by separate modules of similar construction, and thus more economical to fabricate.
Another object of the invention is to provide multi-layered modules for cell culture and related purposes which can be assembled by lamination into an essentially rigid block structure.
Another object of the invention is to provide a cell culture assembly and cell culture system in which the nutrient medium circulation path is independent from the path carrying the cell product, metabolic products from the component of the culture medium and the cells themselves.
Another object of the invention is to provide a cell culture system in which the cells' environmental conditions are continuously monitored and any departures from the desired range of value in any environmental parameter are automatically indicated and corrected.
Another object of this invention is to provide a laminated structure for the fluid paths such that high strength and reliability are attained.
Another object of this invention is to provide a laminated structure that may be increased in size to accommodate large scale cell culture.
Another object of this invention is to provide a cell culture assembly which does not require large volumes of medium.
The aforesaid objects as well as other objects of the present invention will be made more apparent by the following description, claims and drawings.